1. Technical Field of the Invention
The present invention relates to a technology for interconnecting a plurality of phonetic pieces to synthesize a voice, such as a speech voice or a singing voice.
2. Description of the Related Art
In a voice synthesis technology of phonetic piece connection type for interconnecting a plurality of phonetic pieces to synthesize a desired voice, it is necessary to expand and contract a phonetic piece to a target time length. Japanese Patent Application Publication No. H7-129193 discloses a construction in which a plurality of kinds of phonetic pieces is classified into a stable part and a transition part, and the time length of each phonetic piece is separately adjusted in the normal part and the transition part. For example, the normal part is more greatly expanded and contracted than the transition part.
In a technology of Japanese Patent Application Publication No. H7-129193, the time length is adjusted at a fixed expansion and contraction rate within a range of a phonetic piece classified into the normal part or the transition part. In real pronunciation, however, a degree of expansion may be changed on a section to section basis even within a range of a phonetic piece (phoneme). In the technology of Japanese Patent Application Publication No. H7-129193, therefore, an aurally unnatural voice (that is, a voice different from a really pronounced sound) may be synthesized in a case in which a phonetic piece is expanded.